FCC for Beginners

FCC Licensing for Part 90 Land Mobile Radio (LMR) Systems

The Federal Communications Commission (FCC) regulates and licenses use of the radio spectrum in the United States, including Land Mobile Radio (LMR) services. This guide explains how Part 90 Private Land Mobile Radio Services licensing works—from frequency coordination through renewal—and outlines best-practice steps Puget Sound Instrument (PSI) follows to ensure interference-free operation.

1. FCC’s Role in LMR Spectrum Management

Under Title III of the Communications Act, the FCC allocates frequencies and issues station licenses. Technical and operational rules are codified in 47 CFR Part 90, which divides spectrum into two major pools:

  • Public Safety Pool – police, fire, EMS, and related agencies.
  • Industrial/Business Pool – commercial, industrial, and institutional users.

The FCC sets power limits, emission masks, and coordination procedures, and enforces compliance through its Field Offices.

2. Frequency Coordinators and Their Authority

Most Part 90 applications require a certified frequency coordinator to recommend channels before FCC filing (§ 90.175). Coordinators include:

They maintain licence databases, apply engineering criteria to prevent interference, and issue a coordination letter that must accompany the FCC Form 601.

3. Application Process & Technical Requirements

  1. Gather system data
    • Exact transmitter coordinates
    • Antenna height (AGL and/or HAAT)
    • Power or ERP (subject to band-specific caps)
    • Requested frequency pair & emission designator
    • Coverage area / mobile radius & number of units
  2. Coordinate frequencies – obtain the coordinator’s recommendation letter/number.
  3. File FCC Form 601 via ULS – attach coordination letter; pay FCC filing fee (≈ $205) plus coordinator fees.
  4. Await FCC grant – typical processing: 1–2 weeks; longer if objections or waivers are involved.

Conditional Operation (10-Day Rule)

Per § 90.159, operation may begin 10 business days after filing, for up to 180 days, if:

  • The application is properly coordinated and fee-paid.
  • No rule waivers or Canadian/Mexican border coordination are required.
  • Environmental / FAA clearance obligations are met.

4. License Term, Construction & Renewal

  • Term: up to 10 years (§ 90.149).
  • Construction deadline: 12 months to place the station in service and file a construction notification.
  • Renewal window: file 90 days before expiration (§ 1.949). Late filings within 30 days risk a lapse; after 30 days the call sign is cancelled.

5. Penalties for Unlicensed Operation

Operating without a valid license violates § 90.403. The FCC’s base forfeiture is $10,000 per day per unauthorized transmitter; recent PLMR enforcement actions have reached $25,000 plus compliance plans. ([pillsburylaw.com](https://www.pillsburylaw.com/en/news-and-insights/fcc-enforcement-monitor-41.html))

6. Frequency Sharing & Geographic Coordination

Part 90 channels are site-specific; many are shared among multiple licensees separated by distance, terrain, or usage schedule. Coordinators apply contour-overlap criteria; in dense metro areas exclusivity may be justified, while rural areas support closer reuse. Border zones (north of Line A / east of Line C) add international constraints.

7. PSI’s On-Site Spectrum Analysis

Paper coordination can miss undocumented or improperly licensed transmitters. PSI engineers perform field spectrum scans at proposed sites to:

  • Detect hidden incumbents and adjacent-channel spillover
  • Measure real-world noise floor and signal levels
  • Validate frequency choices before deployment

This proactive step exceeds FCC minimums and safeguards clients against surprise interference.

Legal mandate for proactive monitoring

47 CFR § 90.403(e) – “Licensees shall take reasonable precautions to avoid causing harmful interference. This includes monitoring the transmitting frequency for communications in progress and such other measures as may be necessary to minimize the potential for causing interference.”

47 CFR § 90.173(b) – “All applicants and licensees shall cooperate in the selection and use of frequencies in order to reduce interference and make the most effective use of the authorized facilities. Licensees of stations suffering or causing harmful interference are expected to cooperate and resolve this problem by mutually satisfactory arrangements.”

8. Interference Resolution & Legal Compliance Support

Should post-deployment testing reveal that a coordinated channel is in conflict, Part 90 licensees have binding duties to resolve the issue:

  • Cooperate and Resolve: Licensees must “cooperate in the selection and use of frequencies” and work out harmful interference by “mutually satisfactory arrangements.” If that fails, the FCC may impose power, height, or time-of-day restrictions (§ 90.173(b)).
  • Monitor & Cease if Necessary: They must take “reasonable precautions” such as monitoring before transmitting and must modify or stop operation if they cause harmful interference (§ 90.403(e)). Enforcement actions for failing to do so have resulted in fines up to $25,000.
  • Document & Report: The FCC can require detailed measurement reports and corrective timelines, and will inspect stations under § 303(n) of the Act.
  • File Corrective Applications: If coordination proves invalid, the licensee must file a license modification, Special Temporary Authority (STA), or new coordination before resuming full-power service.

How PSI Assists

  1. Rapid Field Diagnostics: Engineers deploy calibrated spectrum analyzers and direction-finding gear to pinpoint offending sources.
  2. Evidence Package: PSI delivers traceable measurement reports, photo logs, and occupancy charts suitable for FCC interference filings or NOV responses.
  3. Regulatory Filings: Our licensing team drafts and submits STA requests, Form 601 modifications, or waiver petitions, liaising with EWA/APCO, the FCC Wireless Bureau, and Enforcement Bureau staff.
  4. Operational Mitigations: Interim measures—adjusting ERP, antenna pattern, or installing filters/combiner hardware—are implemented and re-validated on site.
  5. Mediation & Settlement: PSI brokers technical sessions between the affected parties and their coordinators to reach the “mutually satisfactory arrangement” the FCC expects, avoiding protracted enforcement.

9. References

  • FCC Rules – 47 CFR Part 90
  • 47 CFR § 90.173(b) – Frequency Cooperation Duties
  • 47 CFR § 90.403(e) – Interference-Avoidance Precautions
  • 47 CFR § 90.159 – Conditional Licensing
  • 47 CFR § 90.175 – Frequency Coordination
  • Enterprise Wireless Alliance – enterprisewireless.org
  • APCO International – apcointl.org
  • FCC Enforcement Bureau – PLMR $25 k Fine for Interference (July 2015)

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